Stabilizing Undercoordinated Zn Active Sites through Confinement in CeO2 Nanotubes for Efficient Electrochemical CO2 Reduction

Abstract

Zn-based catalysts hold great potential to replace the noble metal-based ones for CO₂ reduction reaction (CO₂ RR). Undercoordinated Zn (Zn^δ+ ) sites may serve as the active sites for enhanced CO production by optimizing the binding energy of *COOH intermediates. However, there is relatively less exploration into the dynamic evolution and stability of Zn^δ+ sites during CO₂ reduction process. Herein, we present ZnO, Zn^δ+ /ZnO and Zn as catalysts by varying the applied reduction potential. Theoretical studies reveal that Zn^δ+ sites could suppress HER and HCOOH production to induce CO generation. And Zn^δ+ /ZnO presents the highest CO selectivity (FE_CO 70.9 % at -1.48 V vs. RHE) compared to Zn and ZnO. Furthermore, we propose a CeO₂ nanotube with confinement effect and Ce³⁺ /Ce⁴⁺ redox to stabilize Zn^δ+ species. The hollow core-shell structure of the Zn^δ+ /ZnO/CeO₂ catalyst enables to extremely expose electrochemically active area while maintaining the Zn^δ+ sites with long-time stability. Certainly, the target catalyst affords a FE_CO of 76.9 % at -1.08 V vs. RHE and no significant decay of CO selectivity in excess of 18 h.

Keywords: CO; Confinement Effect; Electrocatalytic CO2 Reduction; Undercoordinated Zn Sites.